The Epidemiology Unit was involved in two research projects related to the epidemiology of mycobacterial infections: 1) Epidemiology of NTM in Hawaii: Previous studies identified both Hawaii and Asian-Americans/Pacific Islanders as independently being at increased risk for nontuberculous mycobacteria (NTM) and tuberculosis (TB). To better understand NTM and TB risk patterns in Hawaii, we evaluated data from patients enrolled in Kaiser Permanente Hawaii from 2005-2013. Prevalence was estimated and adjusted odds ratios (aOR) calculated for risk factors. NTM period prevalence was highest in Japanese, Chinese, and Vietnamese patients (>300/100,000 persons), and lowest in Native Hawaiians/other Pacific Islanders (50/100,000 persons). Japanese were two-times more likely than all other racial/ethnic groups to have Mycobacterium abscessus isolated (aOR=2.0, 95% CI=1.2-3.2), but were not at increased risk for other species. In contrast, incidence of TB was stable, and was lowest among Japanese (no cases) and highest among Filipinos, Koreans, and Vietnamese (>50/100,000 persons). Significant differences exist in the epidemiology of pulmonary mycobacteria by race/ethnicity. This may reflect both behavioral and biological factors that affect disease susceptibility. 2) National species distribution of NTM species in the US: we analyzed nationally representative data on NTM species distribution and associated demographic features, using linked microbiologic, clinical, and demographic information from the from PremierTM Healthcare Database. We extracted data for all inpatient and outpatient encounters from 2009 through 201, including all cultures growing mycobacteria regardless of body site sampled for culture. Period prevalence was calculated as the number of NTM-associated patient encounters per 100,000 patients from 2009-2013. Of the 5,928,830 unique patients represented during the 5-year study period, 7,812 (0.13%) had 1 NTM-positive culture. The mean age of NTM patients was 64 years (range: <1-89yrs); most patients were female (52%) and white (70%) and the majority had a respiratory-associated principal diagnosis. Species distribution differed significantly by geographic area. Mycobacterium avium complex (MAC) ranged from 61% of NTM isolates in the West South Central region to 78% in the South Atlantic and East North Central regions and up to 91% in the East South Central region. M. abscessus/M. chelonae ranged from 2% in East South Central region to 18% in West South Central region. Other NTM species, including M. fortuitum, M. kansasii, other rapidly growing mycobacteria, and other pathogenic NTM species, comprised 7% of NTM isolates in the East South Central, compared with 16% in Pacific, 21% in West South Central and 25% in West North Central regions. We found significant geographic variation in species distribution with MAC most common in the South and Northeast and M. abscessus/M. chelonae proportionately higher in the West and South. These species-level differences in regional distribution expands existing knowledge of NTM epidemiology in the US.